Contact spring

ABSTRACT

A filter connector assembly is disclosed which features an electrically conductive contact spring composed of beryllium copper or the like material and having a thin, elongated, and curved central portion of uniform cross-section together with latching tabs or lugs at each end of the central portion. These latching tabs are integral with the central portion of the spring and assume a bent-up position so as to be substantially perpendicular to the plane of the corresponding end part. The connector assembly includes a tubular shaped filter mounted in the assembly; a connector contact pin which is inserted in and may be removed from the central bore of the tubular filter and which may have an external lead connected thereto in any desired manner; and the aforementioned contact spring permanently retained or captivated within the tubular filter after its initial insertion therein. The filter itself takes the form of an inner ferrite tube and an outer ceramic tube closely surrounding the ferrite tube, with appropriately located conductive coatings applied to the surfaces of both tubes. The filter may be of any desired type to give whatever filtering effect is required in a particular application, such as blocking interference signals, modifying pulse waveforms, establishing or changing pass bands for applied signals, etc. The contact spring disclosed herein serves the dual functions of (a) making a stable and constant electrical contact between the conductive coating on the inner wall of the ferrite tube and the contact pin and (b) mechanically holding or securing the contact pin within the central bore of the ferrite tube. Another feature is that the latching tabs or lugs are so shaped and dimensioned as to fit within the ferrite tube bore with a clearance just sufficient to permit initial insertion of the contact spring, the latching tabs then serving to permanently retain the contact spring captive within the filter.

Schor et al.

[111 3,724,834 51 Apr. 3, 1973 [54] CONTACT SPRING [75] Inventors: Ferdinand William Schor, Altadena; Rolland R. Roup, Alhambra, both of Calif.

AMP Domestic Inc., Harrisburg, Pa.

[22] Filed: Feb. 8, 1971 [21] Appl. No.: 113,707

Related US. Application Data [62] Division of Ser. No. 861,299, Sept. 26, 1969.

[73] Assignee:

[52] Cl "267/159 [51] Int. Cl. ..Fl6c 1/26 [58] Field of Search ..267/158, 159

[56] References Cited UNITED STATES PATENTS 2,948,360 8/1960 Lapton ..267/158 3,468,165 9/1969 Sanford ..267/l58 Primary Examiner-James B. Marbert Attorney-Curtis, Morris and Safford [5 7] ABSTRACT A filter connector assembly is disclosed which features an electrically conductive contact spring composed of beryllium copper or the like material and having a thin, elongated, and curved central portion of uniform cross-section together with latching tabs or lugs at each end of the central portion. These latching tabs are integral with the central portion of the spring and assume a bent-up position so as to be substantially perpendicular to the plane of the corresponding end part. The connector assembly includes a tubular.

shaped filter mounted in the assembly; a connector contact pin which is inserted in and may be removed from the central bore of the tubular filter and which may have an external lead connected thereto in any desired manner; and the aforementioned contact spring permanently retained or captivated within the tubular filter after its initial insertion therein. The filter itself takes the form of an inner ferrite tube and an outer ceramic tube closely surrounding the ferrite tube, with appropriately located conductive coatings applied to the surfaces of both tubes. The filter may be of any desired type to give whatever filtering effect is required in a particular application, such as blocking interference signals, modifying pulse waveforms, establishing or changing pass bands for applied signals, etc. The contact spring disclosed herein serves the dual functions of (a) making a stable and constant electrical contact between the conductive coating on the inner wall of the ferrite tube and the contact pin and (b) mechanically holding or securing the contact pin within the central bore of the ferrite tube. Another feature is that thelatching tabs or lugs are so shaped and dimensioned as to fit within the ferrite tube bore with a clearance just sufficient to permit initial insertion of the contact spring, the latching tabs then serving to permanently retain the contact spring captive within the filter.

3 Claims, 7 Drawing Figures CONTACT SPRING This is a division of Application Ser. No. 86l,299 filed Sept. 26, 1969.

BACKGROUND OF THE INVENTION With the increasing use of electronic equipment combined with miniaturization of components and assemblies, the tendency is to crowd considerably more equipment in a limited space than ever before. This condition results in increased electrical interference between equipments to the point where the performance of some of the units is greatly degraded or even rendered useless. Interference between equipments may sometimes be reduced by careful shielding of components and connecting leads. Frequently, it is not practical to shield all of the connecting leads. Also the interfering field may be so great that shielding the leads does not reduce the interference sufficiently. In such cases, it is desirable to provide filters, usually of the low-pass type, at the point where the leads enter the equipment.

One of the most efficient and least expensive ways of providing such filtering is to assemble the filters into the connector receptacle attached to the equipment. In this way, the interfering currents are bypassed to the receptacle shell and return to ground via the outer surface of the equipment chassis. Thus, they are essentially prevented from entering the equipment and causing undesirable interference.

Until recently, the connector filter assembly was constructed with the filter assembled to each contact pin. In addition, the earlier filter connectors were assembled with the filter contact pins locked in place, thus requiring the leads to be soldered to the contacts. with the introduction of multipin connectors carrying hundreds of contacts, it proved more economical to assemble leads to the contact pins using automatic crimping machines and providing a connector construction which allows the contact pin to be pushed into position and locked in place with an internal retention spring. Present filter connectors provide this feature with lockin type filter pins in which the filters are permanently assembled to the contact pin. While these give satisfactory performance, the filter pins are quite expensive and their loss or breakage during lead assembly greatly increases the cost of this operation.

By providing a connector construction in which the filter remains captivated within the connector and only the contact pin is removed, losses due to damaged contact pins during the operation of lead attachment can be greatly minimized. The manner in which this invention permits the use of such a filter connector construction will be described subsequently.

SUMMARY OF THE INVENTION This invention relates to a novel contact spring for use in filter type connectors.

An object of this invention is to provide a means for ensuring constant electrical contact, under conditions of vibration and temperature variations, between the inner contact surface of a filter and a connector contact pin.

Another object is to provide a contact spring which can be inserted into the filter and remain captivated to the filter despite repeatedinsertions and removals of the contact pin.

A further object is to provide surface contact between the spring and the connector contact pin on one side, and line contact between the inner contact surface of the filter and the opposite side of the contact pin, thus providing a low radio frequency impedance between the contact pin and filter, a condition necessary for obtaining the desired filtering action at high radio frequencies.

A stillfurther object is to permit the use of a captivated filter in a filter connector, thus permitting the filter to remain within the connector while the contact pin may be removed and reinserted to permit the attachment of leads by crimping, soldering or other means.

A salient feature of the invention is that the contact spring, when once inserted into the filter, remains locked within the filter unit while permitting the filter unit to be removed from the connector or the contact pin to be repeatedly inserted and removed without affecting the properties of the contact spring. Due to its novel form, construction and spring qualities, the contact spring can be removed from the filter only with difficulty after once being inserted.

Another feature of the invention is that by permitting the filter unit to remain captivated within the connector, only the contact pin is handled during the process of attaching leads, making up-cables and assembling them to the connectors. This feature greatly reduces the possibility of breakage of filters which are composed mostly of brittle ceramic materials. It further greatly simplifies and reduces the cost of automatic lead attachment, a process in which the contact pins are carried on a tape and machine fed to a lead attachmemt tool.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the contact spring of the invention, in a first embodiment thereof;

FIG. 1A is an end view of the contact spring of FIG. 1, showing the outline of the latching tab at the right end of the contact spring as seen when viewed from line lA--1A in FIG. 1;

FIG. 2 is a side view similar to FIG. 1, but of a second embodiment of the contact spring;

FIG. 2A is an end view similar to FIG. 1A, and showing the outline of a modified form of latching tab, viewed from line 2A-2A in FIG. 2;

FIG. 3 is still another end view of the right-hand end of the contact spring in a third embodiment having another modified form of latching tab, this view corresponsing to FIGS. 1A and 2A;

FIG. 4 is a longitudinal cross-section of the filter and showing the contact spring of FIG. 2 captivated within the central bore of the filter, the connector contact pin being removed in this view; and

FIG. 5 is a longitudinal cross-section comparable to FIG. 4, but showing the connector contact pin inserted in place within the filter, the contact spring then assuming the deflected position shown in this view.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 1A, there is shown the filter contact spring 10 of the invention in its simplest form. The spring 10 consists of an elongated, curved central portion 11 of a uniform rectangular cross-section provided with a pair of latching tabs or lugs 12, one

at each end of the spring. Each of the tabs 12 is an integral extension of the central portion 11, bent up into position substantially perpendicular to the plane of the corresponding end part of central portion 11. The springs central portion 11 is made to have a substantial curvature when in its rest or non-deflected position as can be seen in FIG. 1. The central portion 11 follows a uniform radius of curvature which is quite large in comparison to any of the dimensions of the spring itself. The relative magnitude required for the radius of curvature will be specified later, in the description of FIG. 4. The contact spring may be made of any suitable electrically conductive material, such as beryllium copper, for example. The contact spring may be formed from flat wire stock, and heat treated either before or after forming. A suitable finish such as silver or nickel plating followed by gold plating may be provided in order to assure a high quality electrical contact.

FIGS. 2 and 2A illustrate an alternate and preferred embodiment of the filter contact spring 10.

It will be noted that in this version the bent-up latching tabs or lugs 12a are made to be slightly wider than the central body portion 11 of the spring. The relative dimensions required for the end surfaces comprising tabs 12a will be considered subsequently.

FIG. 3 illustrates still another embodiment of the contact spring'featuring a further modified shape for the latching tabs, designated as 12c in this view. In this embodiment the tabs or lugs 120 have a substantially circular contour.

FIG. 4 shows a longitudinal cross-section of the filter assembly with the contact spring 10 in place. The filter consists of a ferrite tube 21 disposed inside a ceramic tube 23. Both the inside and the outside surfaces of the ceramic tube 23 are covered with respective conductive coatings 25 and 26. These coatings which may, for example, be silver coatings are insulated from each other and therefore define a capacitor. It is customary but not always necessaryto split the inner silver coating 25 as by the space 28 so as to form two capacitors. The inner conductive coating 25 is in intimate surface contact with a conductive coating 30 covering both the inner and outer walls of the ferrite tube 21.

When the contact spring 10 is inserted into the filter and locked into position as shown in FIG. 4, its radius of curvature is increased so that the center of portion 11 presses on the insidewall of the ferrite tube 21 at approximately the middle of the tube. This pressure is transmitted through the central portion 11 to the end tabs 12a which bear against the outer ends of the filter in the manner shown in FIG. 4. The tabs 12a, in this case,.are given outside dimensions just large enough so thatthey barely fit into the center bore of thefilter. This construction makes the contact spring 10 almost impossible to remove once it has been inserted in place and achieves a permanent retention of the spring within the filter. With the tabs 12a thus latching or locking the contact spring in place, no amount of vibration, temperature variations, etc. can cause these tabs to become disengaged from the end walls of the filter sufficiently to allow the spring to fall out of the filter. Other importantfeatures are that the tabs have a height such that they do not protrude beyond the outside diameter of the filter; and further that the contact spring does not block the opening at either end of the central bore in the filter and thus permits easy entrance of the contact pin.

In the case of the modified end tabs as shown in FIG. 3, the contour of the tabs and the chord subtended by the bend at each end of the contact spring must be dimensioned to barely fit within the central bore of the filter.

FIG. 5 shows the filter and spring assembly with the contact pin 32 inserted into the filter. When this is done, the contact pin 32 engages and deflects the contact spring 10 until it is practically straight and is exerting substantial pressure against the contact pin. The pressure is usually greatest at the middle of the segment of the contact pin 32 which is enclosed by the filter but is modified by irregularities of the inner wall 30 of the filter. The opposite side of the contact pin is pressed against the conducting inner wall 30 of the filter resulting in continuous electrical contact between these two members. Thus the radio frequency impedance between the contact pin 32 and the conducting inner wall 30 of the filter assembly 21, 23 is maintained at a very low value approaching zero. The pin-to-filter electrical contact requirements for the best possible filtering action are thus fulfilled.

The contact pin 32 can be removed whenever necessary, whereupon the contact spring 10 returns to the position shown in FIG. 4. Note that the assembly as shown in FIGS. 4 and 5 is symmetrical allowing the contact pin 32 to enter with equal facility from either end. This feature permits the filter and spring assembly to be mounted within the connector using either end for the contact pin entry.

It is occasionally necessary in a multi-pin filter connector to replace a filter which has become defective. If such replacement were not possible, it would be necessary to replace the entire connector, an expensive procedure involving considerable labor plus the added cost of a new multi-pin filter connector. With the filter and spring assembly shown in FIG. 4 serving as a replaceable unit in a multi-pin connector to permit filter replacement in accordance with the present invention, it should be appreciated that the captivation of the contact spring 10 within the filter is such as to permit pushing or pulling the filter and spring assembly out through narrow orfices without disengaging the contact spring. Thus, application of the concept of this invention to multi-pin filter connector assemblies permits a far more economical useage of filters within the connector from the standpoint of both initial cost and field serviceability.

Having now disclosed the concept for an improved contact spring for filter pin connector assemblies and various preferred embodiments, the following claims are appended to define what is considered to be inventive: What is claimed is:

1. An electrical contact spring comprising an elongated, narrow curved central portion and integral bentup latching tabs or lugs at each end, said contact spring being arranged to provide constant electrical contact between the inner wall of a conducting cylinder and a contact pin slidably engaged within said cylinder, and said contact spring being dimensioned to permit it to be inserted in said cylinder and to remain captivated therein by said latching tabs or lugs.

3. An apparatus comprising an electrically conducting cylindrically shaped part, pin means for slidable engagement with said cylindrically shaped part, and means comprising an electrically conducting contact spring for making electrical contact between said part and said pin means, said contact spring being formed to remain captivated within said cylindrically shaped part when said pin means is removed from or inserted in said part. 

2. An electrically conducting contact spring comprising a thin, elongated, and curved central portion and integral bent-up latching tabs at each end thereof, said contact spring being arranged to provide constant electrical contact between the inner wall of a tubular conducting cylinder and a pin slidably engaged within said cylinder, and said latching tabs being dimensioned to fit within the central bore of said cylinder with clearance sufficient only to permit insertion of said contact spring, said latching tabs thereby locking the contact spring within the cylinder in a permanent manner.
 3. An apparatus comprising an electrically conducting cylindrically shaped part, pin means for slidable engagement with said cylindrically shaped part, and means comprising an electrically conducting contact spring for making electrical contact between said part and said pin means, said contact spring being formed to remain captivated within said cylindrically shaped part when said pin means is removed from or inserted in said part. 